The present invention includes an improved design for lateral positioning of the stapler body over the anvil. U.S. Pat. No. 2,218,794 (Kilbride) shows a raising spring that operates exclusively for that function, with the body positioned laterally over the anvil in the conventional way using sidewalls of the base as “bearings.” U.S. Pat. No. 6,918,525 (Marks) for a “Spring Energized Desktop Stapler,” whose contents are hereby incorporated by reference, discloses a spacer spring that is stiff in the lateral direction to engage the staple track. The spring provides a forward point for lateral positioning of the track over the anvil by engaging the track. The rear area for such positioning is provided at the hinge connection point between the body and the base. Therefore, the moment arm to position the track laterally is the distance from the tip of the spacer spring, tab 54 fitted in opening 84 of the track, to the hinge connection. The moment arm includes a linkage from the track to the body since the track is mounted in the body. Therefore, the lateral stiffness of the assembly depends on the how rigidly the track is connected to the body. If the track is loose in the body such that it can move sideways in chamber 144 then the utility of a good connection between forward tab 54 and opening 84 is compromised.
A further improvement of the present invention is an automatic opening mechanism for the staple-loading track. In U.S. Pat. No. 5,765,742 (Marks) and U.S. Pat. No. 6,918,525 (Marks), a track chamber includes an elongated cavity exposed at the bottom of the stapler body. The chamber is exposed by pulling a staple track rearward, normally with the stapler oriented upside down so the chamber is exposed upward. In the cited art, a track pull includes extended arms that are squeezed together to release track pull latches. In application '854, the procedure to expose the chamber for loading staples includes three steps: pivot the body up and around the base until the body is upside down, squeeze the arms of the track pull, and pull the track out. Staples are loaded pointing upward, toward the exposed direction of the chamber and pointing away from ceiling 142 of the chamber.
U.S. Pat. No. 4,666,075 (Olesen) shows a traditional stapler track chamber. The body pivots about the base while the staple chamber or track remains over the base. The chamber is exposed in the upward direction. Staples are loaded pointing downward with the points against the “staple stick support bottom 21.”
In a spring powered desktop stapler, one mode of operation includes firing without staples in the chamber. This mode may be called “dry fire.” The striker usually stops near flush with the bottom of the stapler body when a staple is in the chamber and is installed. However, the striker should travel slightly past that position to allow an energy absorbing motion during dry fire. The bottom of the striker can strike parts of the staple-forming anvil in this case. If the bottom of the striker is straight in the conventional way, it could hit the anvil at both the center and the edges of the striker width.
An even worse shape for a desktop stapler striker is shown in U.S. Pat. No. 4,811,884 (Sato). Projections 85, FIG. 19a, are intended to press the staple edges. This design is well known in staple guns. However, in a desktop stapler, such projections would hit the anvil even if the striker did not project past the stapler bottom thus damaging the impacting components.